import 'package:flutter/material.dart';
import 'package:english_words/english_words.dart';

void main() => runApp(new MyApp());

// 来自https://flutterchina.club/get-started/codelab/的HelloWorld程序
class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    // final wordPair = WordPair.random();
    return new MaterialApp(
        title: 'Welcome to Flutter1',
        home: new RandomWords()
    );
  }
}

class RandomWords extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    return new RandomWordsState();
  }
//  @override
//  createState() => new RandomWordsState();
}

class RandomWordsState extends State<RandomWords> {
  // 在Dart语言中使用下划线前缀标识符，会强制其变成私有的
  final _suggestions = <WordPair>[];
  // 字体
  final _bigFont = const TextStyle(fontSize: 18.0);
  // 保存收藏
  final _saved = new Set<WordPair>();

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(
        title: new Text('Open favorite'),
        actions: <Widget>[
          new IconButton(
              icon: new Icon(Icons.list), onPressed: _pushSaved)
        ],
      ),
      body: _buildSuggestions(),
    );
  }

  // 构建单词列表数据
  Widget _buildSuggestions() {
    return new ListView.builder(
      padding: const EdgeInsets.all(16.0),
      // 对于每个建议的单词对都会调用一次itemBuilder，然后将单词对添加到ListTile行中
      // 在偶数行，该函数会为单词对添加一个ListTile row.
      // 在奇数行，该函数会添加一个分割线widget，来分隔相邻的词对。
      // 注意，在小屏幕上，分割线看起来可能比较吃力。
      itemBuilder: (context, i) {
        // 在每一列之前，添加一个1像素高的分隔线widget
        if (i.isOdd) {
          // 奇数行
          return new Divider();
        }

        // 语法 "i ~/ 2" 表示i除以2，但返回值是整形（向下取整），比如i为：1, 2, 3, 4, 5
        // 时，结果为0, 1, 1, 2, 2， 这可以计算出ListView中减去分隔线后的实际单词对数量
        final index = i ~/ 2;
        // 如果是建议列表中最后一个单词对
        if (index >= _suggestions.length) {
          // ...接着再生成10个单词对，然后添加到建议列表
          _suggestions.addAll(generateWordPairs().take(10));
        }
        return _buildRow(_suggestions[index]);
      },
    );
  }

  // 构建列表每一项：图标加文字的
  Widget _buildRow(WordPair pair) {
    // 是否已经收藏
    final _alreadySaved = _saved.contains(pair);

    return new ListTile(
      title: new Text(pair.asPascalCase, style: _bigFont),
      trailing: new Icon(
        _alreadySaved ? Icons.favorite : Icons.favorite_border,
        color: _alreadySaved ? Colors.red : null,
      ),
      onTap: () {
        setState(() {
          _alreadySaved ? _saved.remove(pair) : _saved.add(pair);
        });
      },
    );
  }

  // 打开收藏界面
  _pushSaved() {
    Navigator.of(context).push(
      new MaterialPageRoute(
          builder: (context) {
            final tiles = _saved.map((pair) {
              return new ListTile(
                  title: new Text(pair.asPascalCase, style: _bigFont)
              );
            });

            final divided = ListTile.divideTiles(
                tiles: tiles,
                context: context
            ).toList();

            return new Scaffold(
              appBar: new AppBar(title: new Text("Save suggestion")),
              body: new ListView(children: divided),
            );
          }
      ),
    );
  }
}

//void main() => runApp(MyApp());
//
//class MyApp extends StatelessWidget {
//  // This widget is the root of your application.
//  @override
//  Widget build(BuildContext context) {
//    return MaterialApp(
//      title: 'Flutter Demo',
//      theme: ThemeData(
//        // This is the theme of your application.
//        //
//        // Try running your application with "flutter run". You'll see the
//        // application has a blue toolbar. Then, without quitting the app, try
//        // changing the primarySwatch below to Colors.green and then invoke
//        // "hot reload" (press "r" in the console where you ran "flutter run",
//        // or simply save your changes to "hot reload" in a Flutter IDE).
//        // Notice that the counter didn't reset back to zero; the application
//        // is not restarted.
//        primarySwatch: Colors.blue,
//      ),
//      home: MyHomePage(title: 'Flutter Demo Home Page'),
//    );
//  }
//}
//
//class MyHomePage extends StatefulWidget {
//  MyHomePage({Key key, this.title}) : super(key: key);
//
//  // This widget is the home page of your application. It is stateful, meaning
//  // that it has a State object (defined below) that contains fields that affect
//  // how it looks.
//
//  // This class is the configuration for the state. It holds the values (in this
//  // case the title) provided by the parent (in this case the App widget) and
//  // used by the build method of the State. Fields in a Widget subclass are
//  // always marked "final".
//
//  final String title;
//
//  @override
//  _MyHomePageState createState() => _MyHomePageState();
//}
//
//class _MyHomePageState extends State<MyHomePage> {
//  int _counter = 0;
//
//  void _incrementCounter() {
//    setState(() {
//      // This call to setState tells the Flutter framework that something has
//      // changed in this State, which causes it to rerun the build method below
//      // so that the display can reflect the updated values. If we changed
//      // _counter without calling setState(), then the build method would not be
//      // called again, and so nothing would appear to happen.
//      _counter++;
//    });
//  }
//
//  @override
//  Widget build(BuildContext context) {
//    // This method is rerun every time setState is called, for instance as done
//    // by the _incrementCounter method above.
//    //
//    // The Flutter framework has been optimized to make rerunning build methods
//    // fast, so that you can just rebuild anything that needs updating rather
//    // than having to individually change instances of widgets.
//    return Scaffold(
//      appBar: AppBar(
//        // Here we take the value from the MyHomePage object that was created by
//        // the App.build method, and use it to set our appbar title.
//        title: Text(widget.title),
//      ),
//      body: Center(
//        // Center is a layout widget. It takes a single child and positions it
//        // in the middle of the parent.
//        child: Column(
//          // Column is also layout widget. It takes a list of children and
//          // arranges them vertically. By default, it sizes itself to fit its
//          // children horizontally, and tries to be as tall as its parent.
//          //
//          // Invoke "debug painting" (press "p" in the console, choose the
//          // "Toggle Debug Paint" action from the Flutter Inspector in Android
//          // Studio, or the "Toggle Debug Paint" command in Visual Studio Code)
//          // to see the wireframe for each widget.
//          //
//          // Column has various properties to control how it sizes itself and
//          // how it positions its children. Here we use mainAxisAlignment to
//          // center the children vertically; the main axis here is the vertical
//          // axis because Columns are vertical (the cross axis would be
//          // horizontal).
//          mainAxisAlignment: MainAxisAlignment.center,
//          children: <Widget>[
//            Text(
//              'Andrew have pushed the button this many times:',
//            ),
//            Text(
//              '$_counter',
//              style: Theme.of(context).textTheme.display1,
//            ),
//          ],
//        ),
//      ),
//      floatingActionButton: FloatingActionButton(
//        onPressed: _incrementCounter,
//        tooltip: 'Increment',
//        child: Icon(Icons.add),
//      ), // This trailing comma makes auto-formatting nicer for build methods.
//    );
//  }
//}
